Serge E. Hallyn wrote:> Quoting Andrew Morton (akpm@osdl.org):>> On Thu, 4 Jan 2007 12:12:57 -0600>> "Serge E. Hallyn" <serue@us.ibm.com> wrote:>>>>> A process in one user namespace could set a fowner and sigio on a file in a>>> shared vfsmount, ending up killing a task in another user namespace.>>>>>> Prevent this by adding a user namespace pointer to the fown_struct, and>>> enforcing that a process causing a signal to be sent be in the same>>> user namespace as the file owner.>> This patch breaks the X server (stock FC5 install) with CONFIG_USER_NS=n.>> Neither the USB mouse nor the trackpad work. They work OK under GPM.>>>> Setting CONFIG_USER_NS=y "fixes" this. This bug was not observed in>> 2.6.20-rc3-mm1 because that kernel had user-ns-always-on.patch for other>> reasons. (I'll restore that patch).>>>> There's nothing very interesting here:>[ ... ]> > I can't see any reason for this in the code or comparative ltp runs.> Cedric is testing on a fc6 laptop, hopefully he can reproduce it.

I did reproduce it on a FC5 desktop finally.

get_user_ns() returns NULL when CONFIG_USER_NS=n and this breaks sigio_perm() which does not expect NULL values for ->user_ns.